WASHINGTON - Meteorologists may have found a way to predict some killer heat waves up to three weeks in advance. Now, the best they can do is about 10 days.

Gerald Meehl has co-authored a new study that says an earlier warning would help cities prepare for the heat wave. They can open up cooling centers and arrange checks on the elderly.

The key may be a certain pattern of high and low pressure spots across the globe high in the sky. When that pattern shows up, the chances double for a prolonged and intense heat wave in the eastern two-thirds of the United States.

Meteorologists say this could predict some types of heat waves but not all.